Computers are very powerful tools for searching for relevant information among a vast amount of information. Indexes are a common mechanism for efficiently identifying information of interest among a large corpus of information using a computer. A typical index is an organized mapping of keywords to the documents of information from which the keywords were extracted. As an example, an index of the world's publically accessible web pages may map words in the web pages to the subset of the web pages that contain that word.
Between the actual physical index itself (e.g., the index data as stored on one or more computers) and the users of the system, a search system is typically provided as a software cushion or layer. In essence, the search system shields the user from knowing or even caring about underlying index details. Typically, all requests from users for information in the index are processed by the search system. For example, documents relevant to a user's request for information may be identified by the search system using an index, all without user knowledge of the underlying index implementation. In this manner, the search system provides users quick access to relevant information without concern to how the information is indexed. One well-known search system for identifying relevant information among the world's publically accessible web pages is the GOOGLE Internet search engine provided by Google Inc. of Mountain View, Calif.
One function of a search system is to answer search queries (or just “queries” for short). A query may be defined as a logical expression including a set of one or more search terms, and results in the identification of a subset of indexed documents. Consider, for instance, the handling of a request for information from an Internet search engine. In operation, this request is typically issued by a client system as one or more Hyper Text Transfer Protocol (“HTTP”) requests for retrieving particular search results from indexes on server computers. For example, a request may be for a list of Internet web pages containing the words “college” and “basketball.” In response to this request, the search system typically returns a web page containing hyperlinks to those Internet web pages considered to be most relevant to the search terms “college” and “basketball.”
Internet search engines are well-suited for searching all the world's information that is publically available on the Internet. Recently, however, users are beginning to amass a substantial amount of personal digital information that is not publically accessible on the Internet or indexed by an Internet search engine. Such information can include, for example, personal digital photos, school, and work documents among other personal and private digital information. In some instances, a user's personal digital information is shared with a specified group of users. For example, an employee may share work documents with other colleagues or a user may share digital photos with friends and family.
One way users have recently begun storing and managing all their personal digital information is by using an online content management service. Such services allow users to use their user computers to upload and store their personal digital information on the service's server computers accessible through the Internet or other communication networks. One well-known online content management service is DROPBOX provided by Dropbox, Inc. of San Francisco, Calif.
Users of online content management services would appreciate ways to search for and locate their personal digital information hosted by such services. Such personal digital information is typically not publically accessible on the Internet. For this and other reasons, Internet search engines are generally not adequate to meet the search needs of these users.